Remove nBlockMaxSize from miner opt struct as it is no longer used.

src/miner.h

@@ -158,7 +158,6 @@ public:
     struct Options {
         Options();
         size_t nBlockMaxWeight;
-        size_t nBlockMaxSize;
         CFeeRate blockMinFeeRate;
     };
 

src/test/miner_tests.cpp

@@ -32,7 +32,6 @@ static BlockAssembler AssemblerForTest(const CChainParams& params) {
     BlockAssembler::Options options;
 
     options.nBlockMaxWeight = MAX_BLOCK_WEIGHT;
-    options.nBlockMaxSize = MAX_BLOCK_SERIALIZED_SIZE;
     options.blockMinFeeRate = blockMinFeeRate;
     return BlockAssembler(params, options);
 }